If you think that's old, wait 'til you get a load of this number: 450 million years. That's when the first arachnid was said to have appeared on Earth, based on genetic research recently published in the latest issue of Experimental and Applied Acarology.

I can't even fathom what the earth looked like back then, but seriously, spiders are pretty well equipped for almost any condition. Highly developed senses, self-constructing materials, protective outer armor, and (some) even have a pretty dangerous venom defense system. These guys can live almost anywhere. . . but I try not to think about that when I open my dark closet!